Trump, a leading Republican candidate, dismissed Sanders’ bid for the Democratic nomination during a press conference held at Trump Tower.

He blasted Sanders for what many people saw as his standout moment in the first Democratic debate: defending former Secretary of State Hillary Clinton.

“When the email problem came up, Bernie Sanders lost his whole campaign. I mean, what he did was so stupid from his standpoint,” Trump said.

Clinton, the Democratic front-runner, has for months battled negative headlines about her exclusive use of a private email server and account for her government work at the State Department. Republican candidates regularly hammer her for the controversy, and the FBI is looking into whether any classified information was mishandled.

Trump clearly felt that it was a mistake, however, and he said Tuesday that unless the email controversy spirals out of control, Clinton will defeat Sanders in their primary contest.

“In order to get a one-minute soundbite and some applause, he gave up the emails,” the businessman lamented. “That was the end of his campaign. First of all, people aren’t going to his rallies anymore. “He’s finished. Unless something happens to her with respect to the emails, she’ll easily be the candidate.”